The importance of inventory in making business decisions has been well documented. The business of establishing and managing forests is no different from other businesses. However, forest inventory is very different from traditional business inventory. Joe, of Joe’s Widgets, can come up with a pretty good estimate of how many widgets he has simply by subtracting what he’s sold from what he had in the warehouse or he can simply go to the shelves and count the widgets. Unlike trees, Joe’s widgets aren’t growing larger, being attacked by beetles, or dying from drought.
In forestry, the geographic separation of stands is just the first issue – rarely are all the trees in one contiguous forest. In addition, there’s variability of site quality even in the same stand and resulting variability in growth to contend with. Competition from other woody species growing among crop trees impact growth and impact variability in a stand. Crop trees are all unique in terms of size and quality meaning that it is impossible to conduct 100% inventories by counting identical items as is common in other businesses. Sampling a subset of trees in a stand and sampling a subset of the total number of stands each year is the compromise solution for managers who require information on which to base decisions. Inventory results from previous years must be updated in years when the stand in question is not sampled (see Inventory Updating) to insure a complete up to date inventory annually.
Sampling type (plots, plot size, points, or other methods) makes a difference in the validity of the information collected and the efficiency and resulting cost of the inventory and is all part of inventory design. At Smarter Forestry, we literally wrote the book on forest inventory. Barry Shiver, CEO, of Smarter Forestry is the senior author of the college textbook for forest inventory: “Sampling Techniques for Forest Resource Inventory”. As an example of recent work, Barry designed an inventory to provide product volumes and values on 70,000 acres, across 13 counties, in an inventory that had to be conducted in a month. Rather than design an inventory that required sampling in every stand, the design that was used only required visiting about one third of stands and about 55% of total acres. The inventory was on time and on budget and the resulting estimates had a margin of error of less than 5%.
While efficient design is important, good inventory procedures and follow-up auditing of field personnel insures that a quality inventory is obtained. At Smarter Forestery we insist that foresters conducting the inventory measure rather than ocularly estimate (translation – guess) tree diameters (dbh) and tree heights. We have field personnel measure, and we keep in our databases, dbh to the nearest 0.1 inch. With today’s ever changing and narrow product dbh limits, it is critical to not throw away valuable information that the forester collected (more on this in Inventory Updates).
Experienced. Objective. Tailored. Punctual. Smarter.